A light emitting diode (LED) refers to an element in which minority carriers (electrons or holes) injected using a p-n junction structure of a semiconductor are produced and certain light is emitted through recombination thereof. Light emitting sources are formed through changes in a compound semiconductor material such as GaAs, AlGaAs, GaN, InGaN or AlGaInP so that a variety of colors can be implemented.
The light emitting diodes exhibit properties of less power consumption and longer life span as compared with existing bulbs or fluorescent lamps and can be installed in a narrow space and strongly resist vibration. Such light emitting diodes have been used as display devices and backlights, and studies on application of the light emitting diodes to general illumination have been actively conducted since they are excellent in view of less power consumption and durability. It is expected that their applications will be expanded to large-sized LCD-TV backlights, headlights for vehicles, and general illumination. To this end, it is necessary to improve the luminous efficiency of a light emitting diode, to solve problem of heat dissipation, and to achieve high luminance and high output.
To solve these problems, gradually increasing attention is recently paid to a flip-chip type light emitting device.
FIG. 1 is a sectional view showing a conventional light emitting device with a flip-chip structure.
Referring to FIG. 1, light emitting layers, i.e., an N-type semiconductor layer 5, an active layer 6 and a P-type semiconductor layer 7 are sequentially formed on a predetermined substrate 1. The P-type semiconductor layer 7 and the active layer 6 are partially etched to expose the N-type semiconductor layer 5, thereby fabricating a light emitting cell. Further, an additional submount substrate 2 is prepared and first and second electrodes 3 and 4 are formed thereon, and P-type and N-type solders 8 and 9 are formed on the first and second electrodes 3 and 4, respectively. Thereafter, the light emitting cell is bonded to the submount substrate 2, and a P-electrode and an N-electrode of the light emitting cell are bonded to the P-type and N-type solders 8 and 9, respectively. A molding member (not shown) is formed to encapsulate the substrate with the light emitting cell bonded thereto, thereby manufacturing a light emitting device.
Since the conventional light emitting device with such a flip-chip structure has a higher heat dissipation efficiency as compared with an existing light emitting device and hardly shields light, there is an advantage in that light efficiency is increased by 50% or more as compared with the existing light emitting device. Further, since a gold wire for use in driving a light emitting device is not required, many applications thereof to various small-sized packages have been considered.
However, when the aforementioned light emitting device with a flip-chip structure is driven under a household AC power source, a flicker effect occurs according to on/off at 50 to 60 Hz in the AC power source. Thus, there is cumbersomeness in that an additional auxiliary circuit should be mounted. Accordingly, there is a disadvantage in that manufacturing costs rise due to increases in processing time and costs.